Heat exchangers



United States Patent (1).

3,135,320 HEAT EXCHA GERS Laszlo Forgo, Budapest, Hungary, assignor to Licencla Talalmanyokat Ertkesitii Vallalat,"Budapest, Hungary Filed Mar. 9, 1959, Ser. No. 798,272

I 1 Claim. (Cl. 165-151) and are -split into narrow strips transversally to the direction of the flow. In the known heat exchangers, these fins and strips are made and arranged to form a basic pattern which repeats itself in the direction of flow without variation or change. f -The spacing of the fin strips counteracts the formation .of thick. boundary layers whereby the heat transfer is improved, and a considerable exchange of heat is attained .even at a relatively slow flow and with a relatively low ventilation power. But the use of a fin pattern which repeats itself without variation has a severe disadvantage. The disadvantage appears when the heat exchanger is operated at high flowing speed as it is necessary, for example, in hydrogen-cooled electricity generators or gas turbines. .I have found that, when a certain velocity of flow is exceeded, thevfins start ,to vibrate and produce a high-pitched whistling sound. These vibrations increase the. resistanceagainst the flow and may attain an intensity which makes the use of the heat. exchanger at high flowing speed unfavorable or even impracticable. Tests have shown that the before mentioned whistlelike vibrations are caused by eddies which succeed each other according to the repetition of the fin pattern and eventuallycausethewhole apparatus to vibrate. The

multiplication of the vibrations tends to step up their intensity.

The main objects of my invention are to attain the advantages of fins split into spaced strips while avoiding the above mentioned disadvantage, and to provide a heat exchanger whichhas a-high heat exchanging efficiency, and does notvibrate-at high-flowing speed.

Other objects are to attain these results with simple and inexpensive means, and by a structure that can be easily produced and assembled. Still further objects and advantages will appear from the following description of exemplifying embodiments of my inventiomfrom the appended claims and from the drawings in which .L FIG. 1 shows a broken off view of ,a portion of an embodiment of my invention, the enclosure of the outer medium being omitted, this view being seen in the direction of movement of the outer medium.

FIG. 2shows a view of the portion shown in FIG. '1, seen from the top in FIG. 1.

FIG. 3 shows a cross-section of the portion shown in FIG. 1, taken along line 33 in FIG. 1.

FIG. 4 shows a cross-section of a part which is a modification of a part used in the embodiment FIGS. 1 to 3, this cross-section being seen in the same direction as FIG. 3.

FIG. 5 shows a view seen in the same direction as FIG. 2 and illustrating another variation of the embodiment.

FIG. 6 shows a view seen in the same direction as FIG. 2 and illustrating a further variation of the embodiment.

7 FIG. 7 shows a view seen in the same direction as FIG. 2 and illustrating a still further variation of the embodiment.

FIG. 8 shows a view seen in the same direction as FIG. 3 and illustrating parts which may be used instead of certain parts used in the embodiments illustrated by FIGS. 1 to '7.

FIG. 9 diagrammatically illustrates a complete heat exchanger according to the invention.

The substance of the invention can readily be seen in FIGS. 1, 2 and 3. The basic geometrical structures already referred to, are formed in the direction of flow as indicated by the arrows, by two consecutive fins in each case. The first basic structure consists accordingly of fins 2a and 3, the second of fins 2b and 4 and the third of fins 2c and 5, all of which diverge from each other and by a multiplicity of which the entire heat-transfer surface can; be constructed. I The heat exchanger illustrated in FIGS. 1 to 3 comprises a number of pipes 1 and the medium which has the higher heat transfer coefficient flows in these pipes. These pipes are made of heat conducting material and are heat conductingly connected with fins or thin plates 2 which extend across the space between the pipes. The medium which has the lower heat transfer coefficient flows in this space in the direction of the arrows 33 in FIGS. 2-8 and contacts the pipes 1 and the plates 2. p The plates 2 are likewise made of heat conducting material and are so positioned that their broader sides are parallel to the direction of the flow indicated by the arrows 33. e

Each plate 2 is split into severalnarrow strips by cuts extending across the direction of flow. Some of these strips are indicated by numerals 3, 4 and 5. Thesestrips are pressed out of their original plane. and have different width. The depressed strips remain connected with the remainingparts of the plate 2 by strip portions rising from the ends of their flat bottoms. Other portionsof the plate 2: from strips 2a, 2b, 2c and 2d remaining in the original position between and outside of the depressed strips. The medium flowing in the direction of arrows 3; meets first the strips 2a and 3 whichform a certain patternor configuration characterized by the width of these strips.

Then the flowing medium meets another strip group comprising the strips 2b and 4 whichform a different configuration due to theirdifferent width. The strips 2c and 5 of the next following group have dimensionsdifierent from the corresponding dimensions of the first two groups, a nd hence form a third configuration different from each of the-first two ones. ,1"

.The variation of the strip configuration met successively in the flowing direction is an essential feature of developed or stepped up by a resonance-like effect.

Thereby the development of whistling noise is avoided.

This variation results further in a certain turbulence, amending the heat transfer coeificient of the medium, even at low flowing speed.

.Instead of punching out strips from the plate to one side only as shown in FIG. 3, some strips may be pressed to one side and others to the other side, and instead of pressing out of the original plane only strips alternating with remaining strips, also adjacent strips may be pressed out of the original plane. For example, FIG. 4 shows strips 8 and 10 pressed upward and adjacent strips 6 and 7 pressed downward and have difierent width.

Patented June 2, 1964 In the modification illustrated in FIG. 5, the plate 2 is split along cutting lines which are not parallel whereby the strips 18-24 have surfaces of elongated trapezoidlike shape tapering to different sides and cross-sections which differ from strip to" strip in the flow direction. This type of variation may be combined with the variations illustrated in FIGS. 1 to 4.

' The modifications illustrated in FIGS. 2 and 5 may be combined eg in a manner shown in FIG. 6. There are arranged strips in rows following each other inthe flowing direction of the outer medium, having partly a tapered shape14, 15, 16, 17 and partly uniform width 11, 12, 13. 1 I I The modification illustrated in FIG. 7 has pipes 1 which are arranged'in rows following each other in the flowing direction of the outer medium. For example, there are shown four rows, each comprising two pipes. The pipes of one row are shifted relatively to the pipes of the other row across the flow direction whereby the pipes form a staggered pattern. Strips, some of which are indicated by numerals 25 to 27 and 29 to 31, are punched out from the plate 2 in a manner similar to the modifications described before. These strips extend in directions from one pipe to another pipe of the same row and almost as far as these pipes whereby the strips form a pattern staggered in the flow direction.

A further modification shown in FIG. 7 is that the lines along which the strips are cut are interrupted whereby a portion 28 of the plate 2 is left uncut and separates two pluralities of strips, one comprising strips ending at the fewer pipes may be used. This results in lower manufacturing expenses.

FIG. 8 illustrates a modification in which the heat transferring strips are replaced by heat transferring elements in the form of thin metal rods 32 which are in good heat-transmitting connection with the pipes 1. These rods extend transversely to'the flow direction 33 and are arranged in groups following each other in the flow direction. Each of these groupsdiffers from the other groups by different spacing of the rods, by different cross-sections of the rods, by different mutual inclinations of the rods or by a combination of these features. 1

FIGURE 9 diagrammatically illustrates a complete heat exchanger which comprises the fins as described above. Reference character 1 designates the pipes for conveying the medium of higher heat transfer coefficient,

of which pipes three rows are illustrated by way of ex The v bers 32 0 and 330,respectively, by which the medium flowing inside the apparatus is divided into the individual tubes. This medium enters the collecting chamber 320 in the direction of the lower vertical arrow and withdraws via the collecting chamber 330 in the direction of the upper vertical arrow.

.Instead of providing heat transferring elements according to this invention in the flow of one medium only, similar elements may be provided in the flows of both media. This is, for example, desirable in cases where the media, e.g. two gases, have the same or about the same heat transfer coetficient. I

It will be understood thatmy invention is not limited to the specific embodiments shown: and described, the same being merely illustrative, and that my invention may be carried out in other ways within the scope of the appended claims without departing from the spirit of my invention as it is obvious that the particular embodiments shown and described are only a few of the many that may be employed to attain'the objects of my invention.

What is claimed is:

extending, parallel tubes adapted to receive a first heat medium flowing therethrough, a plurality of longitudimedium of lower heat transfer coeflicient flows in the dinally spaced and opposing plate means fixed to said tubes and extending laterally andtransversely and adapted to receive a second heat medium flowing laterally along the surfaces of said plates, spaced portions of each said plate means being cut and bent from the plane thereof in the form of generally parallel strip means connected at their respective ends to said plate and separated by plate means, the plate means between each pair of successive bent out strip means being also generally in the form-of a plate strip means, all of said strip means being elongated in a direction generally at right angles to the direction of flow of said second heat medium and of length at least several times their width, the extent to which a strip means is bent from the plate means being small in comparison to the stripmeans length, each of said strip means being of uniform width, said bent out strip means being equally displaced from said plate means and being coplanar, the bent out strip means being of diiferent widths so as to vary the frequencies of eddies in the second heat medium and the vibration frequencies ofthe bent strip means and thereby prevent the bent strip means from vibrating in resonancewith each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,606,007 Simpelaar Aug. 5, 1952 2,613,065 Didier Oct. 7, 1952 2,789,797 Simpelaar Apr. 23, 1957 r FOREIGN PATENTS 156,781 Australia May 28, 1954 913,349 Germany June 10, 1954 OTHER REFERENCES Germany, printedapplication G 16773.Ia/17f, Mar. 1, 1956. v 

